A camera module may include an image sensor, a PCB (Printed Circuit Board) configured to deliver electric signals to the image sensor installed on the PCB, an infrared cut-off filter configured to block light in infrared area from being incident on the image sensor, and an optical system including at least one lens configured to deliver an image to the image sensor. Here, a lens driving device configured to perform auto-focus function and handshake compensation function may be installed in the optical system.
The lens driving device may be composed of by a variety of ways. In general, a VCM (Voice Coil Motor) is commonly used in the lens driving device. The VCM operates by an electromagnetic interaction between a magnet fixed in a housing and a coil unit wound on an outer circumferential surface of a bobbin coupled with a lens barrel. The VCM may perform auto-focus function. An actuator module of such VCM may reciprocatively move in a direction parallel to an optical axis while a bobbin being moved in upward and downward directions is elastically supported by an upper and a first elastic member.
Recently, there has been a requirement to develop a lens driving device configured to swiftly detect an optimal focus position by receiving position information of a bobbin installed with a lens as a feedback.
In addition, the control of the lens driving device may encounter a problem, as an internal space of the camera module is becoming narrower according to requirement for miniaturizing the camera module and a shape of an elastic member is formed in response to such requirement.
In addition, the control of the lens driving device may encounter a problem caused by vibration frequency of the elastic member, when the camera module performs auto-focus and handshake compensation operations.
As described in the above, the lens driving device requires a means to control scrambling of the driver. The excessive scrambling of the driver may reduce setting time to cause a problem of lowered auto-focusing speed.